Powered cleaning appliance

ABSTRACT

An autonomous cleaning appliance including a housing, a dirt container disposed in the housing, a brushroll disposed in the housing and configured to move dirt into the dirt container, a brush motor disposed in the housing for driving the brushroll, and a power drive assembly mounted in the housing for propelling the appliance. The power drive assembly including a first drive assembly disposed on a first side of the housing, a first drive motor operatively connected to the first drive assembly, a second drive assembly disposed on a second side of the housing (the second side being opposite the first side), and a second drive motor operatively connected to the second drive assembly. A floor sensor system is coupled to the housing for detecting a loss of floor condition and an off edge condition.

RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser. No. 12/856,238, filed on Aug. 13, 2010, which is a continuation application of U.S. application Ser. No. 12/174,283, filed on Jul. 16, 2008, which is a divisional application of U.S. application Ser. No. 10/967,551, filed Oct. 18, 2004, which claims the benefit of U.S. Provisional Patent Application No. 60/559,186, filed Apr. 2, 2004, the contents of which are incorporated herein by reference in their entirety.

BACKGROUND

Cleaning appliances having a powered drive mechanism are known. For example, many vacuum cleaners include motors to propel the vacuum cleaner across a surface to be cleaned. Some of these vacuum cleaners include a handle to allow a user to maneuver the vacuum cleaner. Other vacuum cleaners are autonomously propelled. Autonomous vacuum cleaners receive directions via a remote signal or they can be programmed to move across a floor.

In addition to automatically propelled vacuum cleaners, sweepers having a powered brushroll are also known. Typically, a motor drives the brushroll. The brushroll rotates and contacts dirt and other debris to propel it into a dust cup located adjacent the brushroll.

SUMMARY

In one embodiment, the invention provides an autonomous cleaning appliance having a housing, a dirt container disposed in the housing, a brushroll disposed in the housing and configured to move dirt into the dirt container, a brush motor disposed in the housing for driving the brushroll, and a power drive assembly mounted in the housing for propelling the appliance. The power drive assembly includes a first drive assembly disposed on a first side of the housing, a first drive motor operatively connected to the first drive assembly, a second drive assembly disposed on a second side of the housing (the second side being opposite the first side), and a second drive motor operatively connected to the second drive assembly. A floor sensor system is coupled to the housing for detecting a loss of floor condition and an off edge condition.

In another embodiment, the invention provides an autonomous cleaning appliance having a housing, a dirt container disposed in the housing, and a power drive assembly mounted in the housing for propelling the appliance. The power drive assembly includes a first drive assembly disposed on a first side of the housing, a first drive motor operatively connected to the first drive assembly, a second drive assembly disposed on a second side of the housing (the second side being opposite the first side), and a second drive motor operatively connected to the second drive assembly. An infrared floor sensor system is coupled to the housing and includes an emitter and a corresponding detector.

In yet another embodiment, the invention provides an autonomous cleaning appliance having a housing, a dirt container disposed in the housing, a brushroll disposed in the housing and configured to move dirt into the dirt container, a brush motor disposed in the housing for driving the brushroll, and a power drive assembly mounted in the housing for propelling the appliance. The power drive assembly includes a first drive assembly disposed on a first side of the housing, a first drive motor operatively connected to the first drive assembly, a second drive assembly disposed on a second side of the housing (the second side being opposite the first side), and a second drive motor operatively connected to the second drive assembly. An infrared floor sensor system assembly is coupled to the housing and includes a first sensor, a second sensor, a third sensor, and a fourth sensor. Each sensor includes an emitter and a corresponding detector. The first sensor, the second sensor, the third sensor, and the fourth sensor are positioned such that when one of the first sensor, the second sensor, the third sensor, or the fourth sensor detects a loss of floor condition or an off edge condition, the infrared floor sensor system delivers a signal to the power drive assembly to stop propulsion of the appliance.

BRIEF DESCRIPTION OF THE DRAWINGS

A powered cleaning appliance can take form in certain components and structures, an embodiment of which will be illustrated in the accompanying drawings.

FIG. 1 is a perspective view of a powered cleaning appliance according to an embodiment of the invention.

FIG. 2 is a perspective view of the powered cleaning appliance of FIG. 1 with a dirt cup removed from the appliance.

FIG. 3 is an exploded view of the powered cleaning appliance of FIG. 1.

FIG. 4 is a cross-sectional view of the powered cleaning appliance of FIG. 6 taken at line 4-4 with the appliance oriented in its use position.

FIG. 5 is another cross-sectional view of the powered cleaning appliance of FIG. 6 taken at line 5-5 with the appliance oriented in its use position.

FIG. 6 is a bottom plan view of the powered cleaning appliance of FIG. 1.

FIG. 7 is a perspective view of a dirt cup for use with the powered cleaning appliance of FIG. 1 with a door of the dirt cup open.

FIG. 8 is a cross-sectional view of the powered cleaning appliance of FIG. 6 taken at line 8-8 with the appliance oriented in its use position.

FIG. 9 is a top view of a cover stop boss and a bumper stop boss depicted in FIG. 8.

DETAILED DESCRIPTION

A powered appliance 10 includes a housing 12, a removable dirt cup 14 located in the housing, a brushroll assembly located in housing, a drive assembly located in the housing, and a bumper 16 mounted to the housing. The appliance 10 will be described as an autonomous sweeper since in the depicted embodiment it does not include a suction source like that of a conventional vacuum cleaner. Alternative embodiments could include a suction source, such as a motor driven fan, that would direct airflow into the dirt cup 14. Furthermore, the appliance 10 will be described as having no upright handle to allow a user of the appliance to direct the movement of the appliance, similar to a conventional upright vacuum cleaner. Nevertheless, if desired, a handle can easily be attached to the appliance for directing its movement.

In the depicted embodiment, the housing 12 of the appliance 10 can be a generally circular plastic casing that encloses internal components of the appliance. With reference the FIG. 3, the housing includes a cover 18 that attaches to a base 22 in a manner that will be described below. The cover 18 includes a rectangular central opening 24 that is shaped to receive the dirt cup 14. A handle 26 attaches to the cover 18 via fasteners 28 and handle clamps 32. The handle 26 can be generally U-shaped and two clamps 32, one at each end of the handle, can attach the cover 18 so that the handle 26 can pivot in relation to the cover 18. The cover 18 also includes a plurality of openings 36 that can be tapered (more clearly visible in FIG. 4) to facilitate attachment of the cover 18 to the base 22 as well as the housing 12 to the bumper 16.

The base 22 of the housing 12 can also be generally circular and include a central cavity 38 that is dimensioned to receive the dirt cup 14. With reference to FIG. 5, the base 18 defines a first brushroll chamber 42 positioned on a first side of the central cavity 38 and a second brushroll chamber 44 positioned on an opposite side of the central cavity 38. A first upwardly angled wall 46 extends from a base wall 48 of the base 18 towards the central cavity 38 and a downwardly angled wall 52 connects to the first wall 46 and the base wall 48. Wall 46 is referred to as upwardly angled because dirt traveling into the dirt cup 14 moves upward in relation to the base wall 48 and through a dirt inlet 54 en route to the dirt cup. With respect to the second brushroll chamber 44, an upwardly angled wall 56 extends from the base wall 48 and connects to a downwardly angled wall 58. The second brushroll chamber 44 also communicates with an inlet opening 62 that communicates with the dirt cup 14. As more clearly seen in FIG. 6, the base wall 48 of the base 18 also includes a large generally rectangular opening 64 between the brushroll chambers to receive a power source for the appliance 10, which will be described in more detail below. A nozzle guard 66 can also attach to the base wall 48 via fasteners 68. The nozzle guard 66 includes a central opening 70 aligned with the opening 64 in the base.

As indicated above, in the embodiment disclosed, the dirt cup 14 is received through the central opening 24 of the cover 18 and in the central cavity 38 of the base 22. With reference to FIG. 3, the dirt cup can include a generally W-shaped housing 72 to which both a dirt cup lid 74 and a dirt cup door 76 mount. The dirt cup lid 74 attaches to the top of the dirt cup housing 72 via conventional fasteners 78 (FIG. 3), or other conventional manners. The dirt cup door 76 mounts to a side of the dirt cup housing 72 and allows for easy emptying of the dirt cup when it gets full. While a W-shaped housing is disclosed, it should be appreciated that the housing could instead by rectangular in cross-section if the power pack of the cleaning appliance were relocated. If this were done the dirt cup could hold more dirt before needing to be emptied.

In the embodiment illustrated in FIG. 5, the dirt cup housing 72 includes an upwardly arched lower wall 82 to accommodate the power source, which will be described in more detail below. The dirt cup housing 72 also includes two inlet openings: a first inlet opening 84 that communicates with the first brushroll chamber 42 and a second inlet opening 86 that communicates with the second brushroll chamber 44. With reference to FIG. 5, inside the dirt cup 14 a first shelf 88 extends inwardly from a lower edge of the first inlet 84 and second shelf 92 extends inwardly from the second inlet opening 86. The shelves 88, 92 help retain the dirt inside of the dirt cup 14 and prevent the dirt from falling out of the inlet openings 84, 86 and back into the respective brushroll chamber.

As most clearly seen in FIG. 7, the dirt cup door 76 hingedly attaches to the dirt cup housing 72 so that it can pivot between an open position and a closed position. A dirt cup handle 94 attaches to the dirt cup housing 72 and can pivot between a stored position (FIG. 1) where the handle is positioned slightly below the dirt cup lid 74 in a recessed area and an extended position, shown in FIG. 2, to facilitate removal of the dirt cup 14 from the housing 12.

As mentioned, the dirt cup 14 can take alternative configurations. For example, in lieu of the door 76, the dirt cup can include a removable dirt cup tray that can slide into the bottom of the dirt cup housing. The dirt cup tray can be removed when the user desires to empty the dirt cup. Other possible configurations include a hinged lid that can open so that the contents of the dirt cup can be dumped out from the top of the dirt cup.

With reference back to the embodiments depicted in the figures, two brushroll assembles are provided to propel dust and dirt into the dirt cup 14. With reference to FIG. 3, a first brushroll motor 102 drives a pinion 104 that engages a toothed belt 106. The brushroll motor 102 rests in a compartment defined in the housing 12, and more specifically in the base 22. The brushroll belt 106 engages a toothed portion of a brushroll dowel 108 that has plurality of bristles 112 extending from it. The brushroll dowel 108 rotates about a brushroll shaft 114 that mounts to an end cap 116. Also adjacent the end cap 116, a brush bearing 118 mounts on the brushroll shaft 114. The end cap 116 mounts inside the first brushroll chamber 42 (FIG. 5) so that the brushroll dowel 108 can rotate within the brushroll chamber. Another end cap and brush bearing are disposed at an opposite end of the brushroll dowel 108 and for the sake of brevity will not be described in further detail. This other end cap also mounts in the first brushroll chamber 42. The nozzle guard 66 sandwiches the end caps into the housing.

A second brushroll assembly made up of a second brushroll motor 122, a pinion 124 and a belt 126 is disposed on opposite side of the housing 12 and the dirt cup 14 as the similar components of the first brushroll assembly. The second brushroll motor 122 also rests in a compartment formed in the housing 12. The belt 126 drives a second brushroll dowel 128 that is disposed on an opposite side of the dirt cup 14 from the first brushroll dowel 108. The second brushroll dowel 128 is disposed in the second brushroll chamber 44 (FIG. 5) in a manner similar to the first brushroll chamber 108 described above and therefore will not be described in further detail. Even though brushroll assemblies have been described as each having a pinion that drives a toothed belt, the brushroll motor can drive the brushroll through interengaging gears or another known transmission.

Turning now to the manner in which the appliance moves across the floor, a drive assembly propels the appliance 10. In the embodiment disclosed, a first drive motor 132 drives a drive sprocket 134 through a gear reduction transmission assembly 136 encased in a gear housing 138 and a gear housing cover 142. In this embodiment, the first drive motor 132 is a reversible electric motor. The drive sprocket 134 engages and drives a toothed drive belt 144, which drives a toothed first track pulley wheel 146. In turn, the first track pulley wheel 146 drives a first belt tread 148 that surrounds the first track pulley wheel 146 and a second track pulley wheel 152 spaced from the first track pulley wheel. The first and second track pulley wheels 146 and 152 receive first and second drive pins 154 and 156, respectively, that attach to the housing 12 so that the pulley wheels are attached to the housing.

A second drive motor 162 drives a second belt tread 164 through components similar to the drive assembly described above. The second belt tread 164 surrounds a first track pulley wheel 166 and a second track pulley wheel 168, both mounted to the housing 12. The second belt tread 164 is disposed on an opposite side of the appliance 10 from the first drive tread 148 and can be driven independently thereof. Such a configuration allows for the appliance 10 to rotate about its central axis easily by driving one motor at one speed while driving the other motor at another speed or, perhaps, in the opposite direction. Because the appliance includes two separate drive assemblies, it can easily turn without the requirement of complicated differential gears and the like. In an alternative embodiment, the appliance 10 need not include the belt treads; instead the appliance could simply include one or more driven wheels that are driven through one or more suitable known transmissions.

Both the drive assemblies and the brushroll assemblies are driven by a power source. A rechargeable battery type power source is disclosed in this embodiment; however, the power source can be any conventional power source including an AC power source from a wall outlet, a solar power source, or a disposable battery power source. As most clearly seen in FIG. 5, a battery pack assembly can fit into the space below the arch shaped lower wall 82 of the dirt cup housing 72. With reference back to FIG. 3, an arch shaped battery pack housing 172 fits underneath the dirt cup housing 72. A removable lower lid 174 selectively attaches to the battery pack housing 172 and a plurality of batteries 176 can fit into the battery pack housing 172. Battery pack contacts 178 are provided to electrically connect the brushroll motors 104 and 122 and the drive motors 132 and 162 to the power source. Also, a charging jack 182 can be provided in electrical communication with the batteries 176 so that the batteries can be recharged.

In the depicted embodiment, the battery pack assembly is centrally located in the base 22 of the housing. If batteries are the desired power source, as mentioned, they can be located elsewhere in the housing, especially if an increase in the size of the dirt cup 14 is desired. As just one example, a set of batteries can be located toward each belt tread 148 and 164 or toward each brushroll chamber 42 and 44. The batteries could also be located elsewhere in the appliance, so long as they electrically connect to the brushroll assemblies and the drive assemblies.

The bumper 16 is movably mounted to the housing 12. In the depicted embodiment, the bumper 16 is a substantially circular shell that at least substantially surrounds the housing 12. The bumper 16 includes a central opening 184 that allows the dirt cup 14 to be lifted away from the housing 12 without having to remove the bumper. Two bottom brackets 186 and 188 are provided to attach the bumper 16 to the housing 12. Each bracket 186, 188 can be a generally rectangular plate having openings that receive fasteners to attach each bracket to the bumper. Fasteners 192 attach the first bottom bracket 186 to the bumper 16 and fasteners 194 attach the second bottom bracket 188 to the housing 16. As more clearly seen in FIG. 6, the first bracket 186 fits into a recess 196 formed in the bottom wall 48 of the base 22 of the housing 12. The recess 196 is generally rectangular in configuration, similar to that of the bracket 186, and is slightly larger than the bracket 186 to allow for movement of the bracket in the recess. Similarly, the second bottom bracket 188 fits into a second recess 198 in the bottom wall 48. The second recess 198 is similarly shaped to and on an opposite side of the appliance 10 from the first recess 196.

With reference to FIG. 3, a plurality of biasing members 202, which in this embodiment are coil springs, attach the housing 12 to the bumper 16. More specifically, the base 22 of the housing 12 includes a plurality of upwardly extending bosses 204 and the coil springs 202 receive the bosses such that the coil springs extend upwardly from the base 22. The tapered openings 36 in the cover 18 of the housing 12 receive the upwardly extending bosses 204 of the base 22 and the springs 202 that are mounted on the bosses. The bumper 16 includes a plurality of downwardly depending bosses 206 that receive the springs 202 so that the bumper 16 is resiliently coupled to the housing 12. In lieu of the coil springs other types of known resilient members, such as flexible plastic members, can be used to attach the bumper 16 to the housing 12.

Movement of the bumper 16 in relation to the housing 12 is limited. With reference to FIG. 8, an extension or a cover stop boss 208 extends upwardly from the cover 18 of the housing 12 towards the bumper 16. A socket or bumper stop boss 210 extends downwardly from the bumper 16 and is received inside the cover stop boss 208. With reference to FIG. 9, bumper stop boss 210 has a diameter slightly larger than the cover stop boss 208 and is aligned concentrically with the cover stop boss 208 when the bumper 16 has no lateral force applied to it. In an alternative embodiment, the cover stop boss could receive the bumper stop boss, such that the socket and the extension arrangement can be reversed. In one embodiment, the radial space between the cover stop boss 208 and the bumper stop boss 210 is less than ¼ of an inch. Accordingly, movement of the bumper 16 in relation to the housing 12 is less than ¼ of an inch in any direction since the cover stop boss 208 and the bumper stop boss 210 are in a concentric circular configuration. With reference to FIG. 2, a bumper supporting ring 212 can attach to a lower edge of the bumper 16.

Movement of appliance 10 can be controlled by sensing the movement of the bumper 16 in relation to the housing 12. In one embodiment, a joystick sensor assembly is disclosed as the sensing device; however, other known motion sensors can be used. With reference to FIG. 5, a lever 214 mounts to a joystick sensor 216 which is an electrical communication with a main printed circuit board (PCB) 218 (FIG. 3). The main PCB 218 can mount to the base 22 of the housing 12 and can be covered by a board cover 222 that attaches the housing 12. Movement of the lever 214 on the joystick sensor 216 can result in a signal being sent from the sensor 216 to the main PCB 218, which can be an electrical communication with the drive motors 132 and 162 to control the movement of the appliance 10. Furthermore, a signal can also be sent, if desirable, to the brushroll motors 102 and 122 in response to movement of the lever 214 on the joystick sensor 216.

The bumper 16 includes a downwardly depending hollow cylindrical boss 224 that is dimensioned to receive the lever 214. Movement of the bumper 16 results in movement of the boss 224 which results in movement of the lever 214. An appropriate signal can be sent to the drive motors in response to movement of the lever. Examples of the types of signals that can be delivered by the sensor are further described in co-pending patent application entitled “Robotic Appliance with On-Board Joystick Sensor and Associated Methods of Operation” filed Sep. 21, 2004, which is incorporated herein by reference in its entirety.

In alternative embodiments, the location of the sensor assembly can be moved. For example, the joystick and lever shown in FIG. 5, can be mounted to the bumper and a boss can extend upwardly from the housing so that movement of the bumper will still result in movement of the lever. The joystick sensor would move with the bumper resulting in the lever moving while the boss would remain relatively stationary. Additionally, other known sensors, such as switch sensors and the like could be mounted to the bumper and/or the housing. For example, movement of the bumper in relation to the housing could activate an on/off type sensor that could deliver an appropriate signal to the main PCB.

Movement of the appliance 10 can also be controlled by floor sensor assemblies 226 that can deliver a signal to the drive motors 132 and 162 via the main PCB 218. As seen in FIG. 6, four floor sensor assemblies 226 can be provided where one floor assembly is located forward the first belt tread 148 and one floor sensor assembly is located forward the second belt tread 164. Also, one floor sensor assembly is located rearward the first belt tread 148, and one floor sensor assembly is located rearward the second belt tread 164. The floor sensor assemblies can include infrared sensors with an emitter and corresponding detector. The emitter can have a field of emission directed downward toward the floor at a location forward or rearward of the corresponding belt tread. The detector can have a field of view that can intersect the field of emission of the corresponding emitter so that off edge and loss of floor conditions can be detected before the robotic appliance, for example, becomes hung up in a depression or tumbles down a staircase. Of course, other types of known sensor assemblies could be used instead, is so desired.

A plurality of switches can be provided to control power to the motors as well as the mode in which the appliance will work. With reference back to FIG. 3, a power button 232 can be provided to activate a push button power switch 234 to control power to the motors. The power switch 234 is an electrical communication with the batteries 176 and the main PCB 218. A biasing member 236 can be provided to bias the power button 232 away from the power switch 234. Additionally, a start button 238 can activate a first momentary switch 242. The momentary switch 242 is in electrical communication with the power source 176 and the main PCB 218 to control power delivery to the drive motors 132 and 162. The start button 238 is biased by a spring 244 away from the momentary switch 242. Additionally, a mode button 246 can activate a second momentary switch 248 to control the mode in which the appliance works. Also, a biasing member 252 can be used to bias the mode button 246 away from the momentary switch 248. The mode button 248 is in electrical communication with the main PCB 218 to control, for example, whether only one brushroll motor or two brushroll motors will be activated. Other modes of operation can also be programmed into the main PCB 218. A plurality of indicator lights 254 can also be provided. The indicator lights 254 can also be in electrical communication with the batteries 176 and the main PCB 218. The indicator lights 254 can light up to indicate different modes of operation.

While the appliance has been described above with reference to certain embodiments, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art upon reading and understanding the preceding description. The above embodiments are intended to be illustrative, rather than limiting, of the spirit and scope of the invention. It is intended that the invention embrace all alternatives, modifications, and alteration that fall within the spirit and scope of the appended claims and the equivalents thereof. 

1. An autonomous cleaning appliance comprising: a housing; a dirt container disposed in the housing; a brushroll disposed in the housing and configured to move dirt into the dirt container; a brush motor disposed in the housing for driving the brushroll; a power drive assembly mounted in the housing for propelling the appliance, the power drive assembly including, a first drive assembly disposed on a first side of the housing, a first drive motor operatively connected to the first drive assembly, a second drive assembly disposed on a second side of the housing, the second side being opposite the first side, and a second drive motor operatively connected to the second drive assembly; and a floor sensor system coupled to the housing for detecting a loss of floor condition and an off edge condition.
 2. The autonomous cleaning appliance of claim 1, wherein the dirt container does not communicate with a suction source.
 3. The autonomous cleaning appliance of claim 1, wherein the floor sensor system delivers a signal to the power drive assembly to affect the propulsion of the appliance.
 4. The autonomous cleaning appliance of claim 1, wherein the floor sensor system includes a first sensor, a second sensor, a third sensor, and a fourth sensor.
 5. The autonomous cleaning appliance of claim 4, wherein the first sensor is positioned forward of the first drive assembly, wherein the second sensor is positioned forward of the second drive assembly, wherein the third sensor is positioned rearward of the first drive assembly, and wherein the fourth sensor is positioned rearward of the second drive assembly.
 6. The autonomous cleaning appliance of claim 1, wherein the floor sensor system includes an infrared sensor.
 7. The autonomous cleaning appliance of claim 6, wherein the infrared sensor includes an emitter and a corresponding detector.
 8. The autonomous cleaning appliance of claim 7, wherein the emitter has a field of emission directed downward.
 9. The autonomous cleaning appliance of claim 8, wherein the detector has a field of view that intersects the field of emission of the emitter such that the loss of floor condition and the off edge condition are detected.
 10. The autonomous cleaning appliance of claim 1, wherein when the floor sensor system detects the loss of floor condition or the off edge condition, the floor sensor system delivers a signal to the power drive assembly to stop propulsion of the appliance.
 11. An autonomous cleaning appliance comprising: a housing; a dirt container disposed in the housing; a power drive assembly mounted in the housing for propelling the appliance, the power drive assembly including, a first drive assembly disposed on a first side of the housing, a first drive motor operatively connected to the first drive assembly, a second drive assembly disposed on a second side of the housing, the second side being opposite the first side, and a second drive motor operatively connected to the second drive assembly; and an infrared floor sensor system coupled to the housing and includes an emitter and a corresponding detector.
 12. The autonomous cleaning appliance of claim 11, wherein the emitter has a field of emission directed downward.
 13. The autonomous cleaning appliance of claim 12, wherein the detector has a field of view that intersects the field of emission of the emitter such that a loss of floor condition and an off edge condition are detected.
 14. The autonomous cleaning appliance of claim 11, wherein when the infrared floor sensor system detects a loss of floor condition or an off edge condition, the infrared floor sensor system delivers a signal to the power drive assembly to stop propulsion of the appliance.
 15. The autonomous cleaning appliance of claim 11, wherein the infrared floor sensor system includes a first sensor, a second sensor, a third sensor, and a fourth sensor, each of the sensors including an emitter and a detector.
 16. The autonomous cleaning appliance of claim 15, wherein the first sensor, the second sensor, the third sensor, and the fourth sensor are positioned such that when one of the first sensor, the second sensor, the third sensor, or the fourth sensor detects a loss of floor condition or an off edge condition, the infrared floor sensor system delivers a signal to the power drive assembly to stop propulsion of the appliance.
 17. The autonomous cleaning appliance of claim 11, wherein the infrared floor sensor system includes: a first sensor positioned forward of the first drive assembly, a second sensor positioned forward of the second drive assembly, a third sensor positioned rearward of the first drive assembly, and a fourth sensor positioned rearward of the second drive assembly.
 18. The autonomous cleaning appliance of claim 11, wherein the infrared floor sensor system communicates with the first drive motor and the second drive motor via a printed circuit board.
 19. The autonomous cleaning appliance of claim 11, wherein the infrared floor sensor system is positioned on a bottom side of the housing.
 20. An autonomous cleaning appliance comprising: a housing; a dirt container disposed in the housing; a brushroll disposed in the housing and configured to move dirt into the dirt container; a brush motor disposed in the housing for driving the brushroll; a power drive assembly mounted in the housing for propelling the appliance, the power drive assembly including, a first drive assembly disposed on a first side of the housing, a first drive motor operatively connected to the first drive assembly, a second drive assembly disposed on a second side of the housing, the second side being opposite the first side, and a second drive motor operatively connected to the second drive assembly; and an infrared floor sensor system coupled to the housing and including a first sensor, a second sensor, a third sensor, and a fourth sensor, each including an emitter and a corresponding detector, wherein the first sensor, the second sensor, the third sensor, and the fourth sensor are positioned such that when one of the first sensor, the second sensor, the third sensor, or the fourth sensor detects a loss of floor condition or an off edge condition, the infrared floor sensor system delivers a signal to the power drive assembly to stop propulsion of the appliance. 